(All)north district – relief
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(All)north district – relief

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  • Private land developer and government continue change the use of land in north district, agricultural land was converted into car park, high-rise buildings and Container yard etc. Land area use to dredge water greatly reduces due to the reconstruction of land. Natural land has been paved by hard surface. Lead to rainfalls flow into the river directly. In order to continence the work of drain flooded, government connect the drains directly from Sheung Shui, Fanling Town Centre to Ng tung river, however do not widen the river channels or open another channels, it leads to problem of flooding
  • Rivers in Hong Kong are generally short and small, without a distinctive middle course. Typically, the upper course is steeper, the middle one gentle while the lower course is nearly flat The upper course includes the headwaters of a river, As the upper course is steep, many narrow, V-shaped valleys are formed by the prevailing downward erosion, With proper geological conditions, waterfalls form along the upper course. Ng Tung Chai waterfalls, Bride's Pool waterfalls and Man Cheung Po are all tourist hotspots with waterfalls in Hong Kong The lower course is the section with most abundant water flow, it is a flat terrain, Sediments from the river are carried to the river mouth, where they may form an delta, is easy cause flooding, During floods, the rivers overflow their banks, carrying sediments that are deposited to form the floodplain. In Hong Kong, the largest floodplains are at Yuen Long, Kam Tin and Sheung Shui.
  • Based on the distribution of tributaries, local rivers can be mostly classified into three drainage patterns: dendritic, rectangular and radial.
  • Tributaries from the upper course merge with the main stream at fairly regular intervals. The angle between the major channel and its tributaries is less than 90 degrees, similar to that between a tree trunk and its branches the major channel and its tributaries are connected at angles close to 90 degree. This can occur if faults and joints in the bedrock are arranged at right angles, so rivers and streams flow and erode along these lines of weakness Radial drainage patterns comprise several streams that diverge from the same point. Streams and rivers often radiate in all directions from the peaks of mountains.
  • 淹浸農田、房屋,居民在屋頂等待救援 Sham Chun serves as the natural border between Hong Kong and Mainland China , together with the Sha Tau Kok River .
  • http://paper.wenweipo.com/2007/05/18/HK0705180021.htm
  • 隨著深圳河治理第一期、第二期和第三期工程分別於 1997 年年中、 2000 年年中和 2006 年底完成後,新界北部沿深圳河與平原河匯合處的低窪地帶的水浸情況已大大得到改善 渠務署終落實在二○一三年,在深圳河上游近香園圍一段,展開最後一期治理工程,預計二○一七年完工 With the Shenzhen River’s Regulation work stage 1, 2 and 3 finish on mid 1997, 2000 and 2006. the confluence of New Territories and shenzhen’ low-lying areas the situation has greatly improved
  • 足以抵禦 50 年一遇的洪水。 淤泥的問題,並就深圳河的 水質問題 提上議程 The place of construction is between, HK zH must have a good communication.
  • In the following session, I will introduce the climate in Hong Kong. 
  • Let me introduce the background of climate in Hong Kong. Do you know where Hong Kong locate? Southern hemisphere or Northern hemisphere? Yes, the answer is Hong Kong is located at Northern hemisphere. It is very close to equator, and hence Hong Kong is belongs to humid subtropical climate condition.
  • Let's see this map. This dotted line is equator and the blue pin is the location of Hong Kong. You see, Hong Kong is close to the equator.
  • Let's move on to the following seesion, weather in Hong Kong. As I mentioned before, Hong Kong is belongs to humid subtropical climate condition. According the record, the average temperature in Hong Kong is about 22.7 degree C, and the annual rainfall is 3066.2mm at 2008. Hong Kong is a warm city, the temperature range is not so large and there is no snowfall in  winter.
  • Summer is a rainy season, it occur between May to October. In Hong Kong, there are three Rainstorm warning system namely amber, red and black. When there is red or black rainstorm signal is announced, some region may cause flooding. For example, Northern New territories and low-lying area. Since the drainage system is overload, the rain water can not transfer to the river and cause serious flooding. It is very dangerous. The drainage system will be mentioned in next session.
  • When Hong Kong enters to May, the trough, precipitate and typhoon started to bring toward to Hong Kong.  The trough came across to southern China and cause heavy rain.  The precipitate also produce heavy rainfall. ==================== During May to June, September to October, 其次是地形雨和鋒面雨,地形雨是指潮濕的向岸風一旦遇上高山便迫使空氣上升,達至凝結高度和成為降雨。鋒面雨則是指冬季當有冷鋒橫過香港時,暖濕的空氣被冷乾的空氣底切而上升,引致降雨。 http://www.weather.gov.hk/wxinfo/pastwx/ywx2005c.htm http://hk.knowledge.yahoo.com/question/question?qid=7006112804506
  • Besides the above factors, the global warming, El nino and La nina are affecting Hong Kong. Global warming is a worldwide impact across the world. It is mainly caused by the human activities like burning fossil fuels, industrial activities, and so on. Those activities results in produce excessive Carbon dioxide and cause global warming. For El nino and La nina, they are related to global warming too because global warming enhance them.
  • From this chart, it shows that El nino and La nina can cause extra rainfall than the normal weather.
  • So what is the human factors increase the rainfall?  There are some reasons like industrial activities, deforestation, excessive greenhouse gases. They are causing the temperature increase, hence they produces more rainfall.
  • Common target, reduce the emission of CO2

(All)north district – relief (All)north district – relief Presentation Transcript

  • Li Tsun Sang 52621940 Ng Tsz Wa 52622020 Chow Lai Yin 52621822 Tam Chun Man 52379840 Lam Kwok Tung 52610985
    • surface water > carrying capacity of the channel
    • exceed bankfull stage
    • inundation occurs at flat ground (flood-plain) alongside the river banks
    • Blackspot Scales:
    Small - affecting area >0.25 hectares  agricultural damage , isolated property damage/ traffic disruption Medium - affecting area > 10 hectares  significant property damage/ serious traffic disruption Major - affecting area > 100 hectares  serious socio- economic disruption Source: DSD
  • Source : DSD
  •  
    • Causes of flooding
    • Measures taken by government to tackle flooding
    • Evaluation of gov.’ s effort and suggestion
    Natural factors Weather Catchment features Human influence
  •  
    • Hong Kong has no large rivers.
    • The larger rivers are mainly in the northwest, including: Shan Pui River, Shenzhen River, Kam Tin River, Sheung Yue River, and Ng Tung River.
    • Mountain
    • Low lying
    • Private land developer and government continue change the use of land in north
    • Land area use to dredge water greatly reduces due to the reconstruction of land.
    • In order to continence the work of drain flooded, government connect the drains directly from Sheung Shui, Fanling Town Centre to Ng tung river
    • Rivers in Hong Kong are generally short and small, without a distinctive middle course.
    • Upper course - steep, many narrow, V-shaped valleys are formed by the prevailing downward erosion
    • Lower course - flat terrain, it is easy cause flooding
    • From the distribution of tributary(river), three kind of shape are list below :
    • Dendritic Drainage Pattern
    • Rectangular Drainage Pattern
    • Radial Drainage Pattern
    • Dendritic Drainage Pattern
    • the most common drainage pattern
    • in Hong Kong
    • e.g. Lam Tsuen River
    • Rectangular Drainage Pattern
    • Appear at regions of the western New Territories
    • e.g. the upper course of Tuen Mun River
    • Radial Drainage Pattern
    • found on roughly conical mountains
    • e.g. Sunset Peak
    • Longest river in Hong Kong
    • Dendritic Drainage Pattern
    • Between New territories and Shenzhen
    • Early 90s, lots rainfall lead to flooding
    • Total four Regulation work of Shenzhen River
    • Main source of flooding in Hong Kong
    • Bend, meandering taking place
    • Poor drainage of water
    • Depth of water increase from 3m to 7m
    • Straight
    • lower course flow has upgrade
    • Thread of flooding Eliminate
    • The problem of flooding reduce.
    • Amount of silt bring the problem of flooding again
    • Poor maintenance
  •  
      • Located at northern hemisphere
      • Close to Equator
      • Humid subtropical climate condition
    • Equator
    • Hong Kong
      • Humid subtropical climate
      • Average temperature: 22.7 °C
      • Annual rainfall: 3066.2mm (at 2008)
      • Summer is a rainy season
      • some region in northern N.T. and low-lying area cause serious flooding
      • the drainage system is overloaded.
      • The rainfall is mainly came from typhoon, trough, precipitation
      • During summer, trough came across southern China and bring heavy rainfall produce
      • Precipitation also produce rainfall
      • Global warming
      • El nino
      • La nina
    • Increase annual rainfall by El nino and La nina
    • Year of El nino
    • Year of La nina
    • Normal Year
    • .
    • rainfall (mm)
  •  
  •  
      • Industrial activities
      • Deforestation
      • Excessive greenhouse gases (especially CO2)
      • Increase in temperature
      • Flooding Warning System
      • The government policies can not show the effect in a short period
      • It is no evidence to support there are any significant improvement
      • Cooperate with other countries
      • Set up the rules to limit the emission of carbon dioxide
      • Educate the concept of protect the city to citizens
      • Cooperate with other countries
      • Set up the rules to limit the emission of carbon dioxide
      • Educate the concept of protect the city to citizens
  • Human influence
  • Construction
    • Many constructions of rivers and channel operating in North New Territories
    • Some constructions need many years to finish
  • Construction
    • Kind of waste or barrier at riverbed
    • Industrial waste
    • Sand , stone and mud
  • Construction
    • The roads are paved with sand and stones
    • Dug from the riverbed
    • Not be held tightly
    • Wash away easily
    • Clog up the river and channel
    • Decrease the velocity of water flowing
  • Sha Po Tsai Village accident
    • Serious accident causing death in 2010
    • The river constructions near
    • found many industrial barriers and big stones after flooding
    • maybe caused by the
    • construction
  • Deforestation or removal vegetation
    • Removal of trees near the river
    • Solid is washed away easily
    • River bank collapses
  • Sha Po Tsai Village accident
    • One of the branches in the village is blocked by the construction
    • The rainstorm water cannot be drained out
  • Ownership of the place
    • Rural village
    • Some private places cannot be built with channel
    • No right to clean up and repair
    • Not enough regulation of use of rural place
    • incomplete drainage system
  • Ownership of the place
  • City planning and developing
    • Many natural rivers in New Territories
    • Need to develop and construct channel
    • Channel need to be changed or designed into narrow or bend
    • Avoid the buildings or facilities
    • Lower the strength of draining out water
  • City planning and developing
    • Surface is made with concrete
    • Increase water flowing on the surface
    • Water cannot be held
    • Stored in the farm, pond, underground or other
  • City planning and developing
    • Yeun Long
  • Result
    • Rivers are destroyed and cut down
    • Channels are not able to handle the rainfall
    • Drainage system cannot drain the rainfall effectively
  •  
    • Drainage Channels
    • Flood Pumping
    • Flood Storage
    • Shenzhen River
    • Ng Tung River
    • Sheung Yue River
    • Ma Wat River
  •  
  • Before the improvement
    • Flooding was always appearing in NNT when a rainstorm came
    • Flooding was risked who living in low-lying area
  • After the improvement
    • The repaired Shenzhen River section required a drainage capacity that can resist a 50-year return flooding
    • The flooding problems in Sha Tin, Fanling, Sheung Shui and Ta Kwu Ling area can be resolved.
    • Collect rainwater within the village
    • Pump out the water collected in the pond
    • Convey the water to a floodwater from storage pond
  •  
    • Flooding situation in the NNT has been alleviated because of the 4 main channel were rehabilitated and the flood pumping has been completed
    • Around 30,000 people who live in low-lying are being protected
    • Flooding problem have not totally complete
    • Increasing the flood pumping station
    • Installing additional drainage pipes
    • Installing additional grilles that can reduce the possibility of blockage
  • “ In 2008, drainage improvement works along Ma Wat River in NNT was substantially completed. The level of protection against flooding at Kau Lung Hang has been raised.” adapted from DSD 07-08 annual report Then, in 2011…
    • “ Recognising the aspirations of the public for greening to enhance quality of life and to help protect the environment, the DSD places great emphasis on the greening of drainage channel…”
    • “ One of these examples is the 'Drainage Improvement for Ma Wat River at Kau Lung Hang' where large-scale greening work has started.”
    • DSD Newsletter (09/04/2011)
    • Criticism:
    • channel project carried out without comprehensive planning (e.g. lack of beautification work)
    • extra cost incurred in redundant greening work
    • Government should consider all aspects before implementation of the project
    • Consultation on experts from different fields (e.g. engineers, environmentalists)
    • Consultation on public (esp. local residents)